Gas lift oil recovery system



Jam/26, 1943. R. L.. KIRKPATRICK 2,309,512

GAS LIFT OIL RECOVERY SYSTEM Filed March 21, 1941 3 Sheets-Shee' l 4r Y f v l 1111111 i .rinda hl .v i. Y j, U nuL M L \m I if ff r 7 u, O 7 7 Q Jan- 26, 1943- R. L. KIRKPATRICK 2,309,512

' GAS LIFT 011. RECOVERY SYSTEM Filed March 21, 1941 1 s sheets-sheet 2 g5 15mm-ow PRESSU RE REGULATOR Jan. 26, 1943. R. l.. KIRKPATICK 72,309,512 A i GAS LIFT OIL RECQVERY SYSTEM -Filed Maron 21, 1941 s sheets-sheet s ,ywp'catq /60 33 xi I /75 f Z6 e -26 C" 7 6i 2, 84.1 85

hunted Jan. 26, 1943 2,309,512 GAS LIFT on. RECOVERY SYSTEM Robert L. Kirkpatrick, Verona, Pa., assignor to Gulf Research & Development Company, Pitts burgh, Pa., a corporation of Delaware Application March 21, 1941, Serial No. 384,559

9 Claims.

This invention or discovery relates to gas lift oil recovery systems; and it comprises in an intermittent gas lift system for wells having the usual string of tubing extending down the Well, a gas control valve in the lower portion of the tubing, a reciprocable member for alternately opening and closing the control valve and vpower means for reciprocating said member, the improvement comprising an electrical control circuit for the power means, including a float switch in fixed relation to the reciprocable member and arranged for operation by well liquid rising in the tubing to the level of the float switch so as to cause actuation of the power means upon rise of liquid to said level; all as more fully hereinafter set forth' and as claimed.

A good modern type of intermittent gas lift oil recovery system makes use of a string of tubing extending from the top of the well down into the liquid in the well, and fitted with a lower standing valve and one or more gas inlet control valves in the tubing wall thereabove. The tubing is packed off below the control valve, and gas under pressure is maintained in the space outside the tubing. Oil flows into the lower Ipart of the tubing under formation pressure. At regular (constant-rate) intervals the gas control valve is opened, by means of a sinker extending down to it on a cable, to start a slug of oil toward the surface. When the slug reaches the surface, the control valve is caused to close, and the cycle is repeated.

Such systems give good results if the control valve closing and opening intervals are correctly adjusted, but if the intervals are not correct the eciency may be low. The correct operating rate is determined by trial and error; a tedious and difficult procedure in some cases. Moreover the adjustment; is thrown out if the rate -of inilux of oil from the well varies, as often happens.

Proposals have been made for controlling gas lift systems with the aid of a iioat switch located in iixed relation to the tubing, but in such systems, if it is desired to change the effective level of the switch the entire string of tubing has to be withdrawn and reinstalled with the switch in a new position; a tedious and diiiicult operation.

Among the objects of the present invention are the provision of a gas lift system of the Atype described, in which means are provided for actu ating the gas control valve in accordance with rise of liquid in the tubing to a predetermined level, thereby assuring maximum operating eflciency; and the provision of such a system in which the predetermined operating level is readily changed with a minimum of complication.

These and other objects are achieved by the provision of an electrically controlled gas valve operating device in such systems, and-a float switch, in fixed relation to the reciprocable sinker, and adapted to actuate the operating device on rise of liquid to the level of the float switch. This level is readily determined by changing the spacing of the oat switch; an operation requiring merely withdrawing the iloat switch and sinker and putting in a new suspension of dif ferent length.

In the accompanying drawings I have shown diagrammatically two examples of specific embodiments of apparatus Within the purview of the invention. In the drawings:

Fig. l is a view partly in elevation, partly in central vertical section, of the portion of one form of the apparatus which is installed in a well,

Fig. 2 is a similar View of a modiied form,

Fig. 3 is a view in elevation of the part of the apparatus of Figs. 1 and 2 which is installed above ground, and

Fig. 4 is a detailed view partly in elevation and partly in central vertical section of one form of perforate cage containing the iloat and float actuated tip switch.

Fig., 1 shows the invention applied to a gas lift-. system including a string of eductor tubing *i0 extending down a well cased at il and ter minating at a casing head (Fig. 3). The tubing and casing denne an annular space I2 down which gas is pumped. String l0 is joined at I3 to an enlarged section ld communicating with a gas control valve tting i5 the valve it of which is opened and closed by a reciprocable sinker l'l. The valve is shown in open position, depressed by the sinker. Fitting l5 communicates through a standing valve I8 with a bull plug fitting i9 extending into the well liquid (not shown) and packed off at 20. The sinker is reciprocated from the surf-ace through the agency of a piston 22 and a lifting cylinder 2l suspended directly over the casing head (Fig. 3).

The use of the packer 2G is not always necessary but depends rather on the liquid level or bottom hole pressure in the well. If the liquid level in the well is high, a packer neednot be used but if it is low a packerris" necessary to prevent blow-by of the operating gas around the bottom of the tubing and to withhold operating gas pressure from the reservoir of oil so that it will not seriously oppose the ow of oil into the well.

Sinker Il is attached through a cable 25 to a perforate cage 26 containing a float 2l freely movable therein and adapted in its upper position to close a mercury tip switch 23, this construction being shown. diagrammatically in Figs. 1 and 2 and in detail in Fig. 4. The cage and the sinker are reciprocated by a double electrical cable 29 attached to the cage and in electrical connection with the switch. The cable extends through a stuiiing box 3u on the casing head to a clamp 3| attached to the piston rod 32 of piston 22.

Gas under regulated pressure is introduced into the casing head at inlet 35 and liquid and gas are discharged from the well at outlet 35.

The lifting cylinder 2| is operated on the upstroke by gas pressure from 35, and on the downstroke by gravity. Admission of gas is controlled by a three way pneumatic valve 36 having two diaphragm power means 3l and 38 as shown, and adapted in one position to admit gas t cylinder 2| from fitting 35, through conduits 39 and 4U, and in its other position that shown) to exhaust the cylinder thr'ough conduit :i3 and vent 4|. able to the right by pressure at diaphragm 33 through a branch conduit 42, as shown, and shiftacle to the left by pressure from outlet fitting 3S, applied to diaphragm r3l through a conduit d3. Branch '42 has a restricted-orice tting 50, a pressure regulator |50 and a bleedofi vent #it normally open but closable by a weighted lever valve 45 on energization of a solenoid 46 operating on one end of the lever valve as shown.

The wires of cable 2S are in circuit with a source of electrical energy shown as a battery d?, a switch openable at the top of the piston upstroke and the solenoid S.

The appara-tus operates in a cyclic manner as follows:

Liquid flows into the tubing through fitting I9 and rises to cage 26, causing the float to close the tip switch. Switch 153 being closed at this time, solenoid el? is energized by battery lll oldsing bleed-ofi Pressure builds up at diaphragm 38, moving the valve |36 to position such that gas under pressure flows through 39 and il and raises piston 22. rlhis lifts sinker Il into the position shown in Fig. l, opening valve lB for admission of gas into the body of liquid in the tubing. At the top of the stroke of piston 22, switch 48 isopened, thereby opening bleed-ofi lill. Pressure is released vfrom diaphragm 33. To ensure proper release, the effective orice of the bleed-off is made larger than that of orifice tting 5G.

With the opening of valve I6 a slug of liquid not shown) is started to the surface. When it reaches the well head and ows out through outlet 36 its pressure is transmitted to diaphragm 3l, through duct 43, thus causing the three-way valve to shift to the position shown in Fig. 3, venting lift cylinder 2|. The piston moves downward, valve I6 closes and the cycle is completed. When liquid again builds up to the level of the oat switch, the cycle is repeated.

The distance between the sinker l1 and the cage 26 determines the amount of liquid for each slug. If it is desired to change the amount of liquid per slug it is merely necessary to withdraw cable 29 which carries the cage and the ascetic sinlrer, and rit a new suspension 25 of different length. In some installations a plurality or gas control valves are provided at spaced intervals up the tubing, all operated by a reciprocable sinker in a manner similar to that described. The present improvement ls applicable to such systems, and in such cases the location of the sinker may be changed simply by changing the distance between the float switch and the sinker where there is sufficient gas pressure for lifting larger slugs of oil, or by progressively lowering the switch and sinker to the particular control valve at which it is desired to operate.

In Fig. 2 I have shown a modified form of apparatus which has advantages in some utilizations. Gas is introduced at the top of an accumulation chamber, to force liquid down the outside and then up inside the eductor tube; an arrangement which results in more solid slugs of liquid, so to speak, than when gas is merely' introduced into the bottom of a charge of liquid in the usual way. As shown, tubing l0 is connected through a concentric enlarged section 55, defining an annular passage 56, to a bull plug 6| and standing valve I8. A control valve 53 is provided in section 55, adapted to be opened on the upstroke of a hollow, tubular sinker 5l to admit gas into passage 55. Actuation of valve 58 by the sinker is through a reciprocable operating pin |58 positioned opposite the valve in the wall of the tubing IU. Section 55 is packed oli at 62 below the valve. The lloat switch as sembly 26, 2l, 28 is suspended below the sinker, as shown. If desired the float switch assembly and the sinker may be incorporated in a single unit.

In operation, liquid builds up in the annular space 56 and tube to the level of the float switch, whereupon sinker 5l is raised to open valve 58 through reciprocation of pin |58 and gas is introduced on top of the liquid charge in the annular space. A slug of liquid is there by started on its way to the surface. The operating cycle of the apparatus of Fig. 2 is like that of Fig. l.

Fig, 4 shows one form of construction of perforate cage, lioat, and float actuated tip switch assembly useful in the practice of the present invention. In this showing, cage 26 consists or a section of metal tube closed at its lower end and provided with perforations l5 in its side walls. The upper end of the tube is threaded to receive cable socket 16 in which cable l? ls secured in conventional manner as by swedging, leading or the like. Clamped between the top of the cage and an internal shoulder '58 on the cable socket is a threaded plug 'i9 through which the electric wires B0 of the cable pass into the cage and connect with the switch as shown. The mercury tip switch 253. of conventional in sulated construction, is supported by a pair of yoke members 8| and 82 respectively, formed of ber or other non-conducting material. Yoke 8|, as shown, is shorter than yoke 82 and is piv' oted at 83 to a bracket secured to the wall of the cage. The longer yoke member 82 projects from below the switch to a position where it may be struck by the iioat 2l'. The float consists simply of a hollow sealed cylindrical metal can.

,Since the upward travel of the float need be sufcient only to close the switch by tilting it about pivot 83, stops 84 secured to the side walls of the cage are provided for engaging the top end of the float opposite its reduced end 85 for limit. ing upward travel.

In all embodiments the slug of liquid is started to the surface only when the liquid has built up to a predetermined level. This insures delivery of the maximum desired (or maximum permissible) slug at each cycle. If the rate of inilux of oil from the well to the tubing varies, the time period for each cycle varies correspondingly, always insuring complete eiiiciency.

What I claim is:

1. In a gas lift pump of the type wherein a wire line suspended sinker is alternately raised and lowered in a well for'controlling the operation of bottom hole gas valve including means forY raising and lowering the wire line and sinker, the improvement which comprises, an electric circuit including a source of electricity, electrically operated means for controlling the movement of the Wire line in one direction and a pair of switches in series electrical connection with the source of electricity and said electrically operated means, one of said switches being adjustably suspended in the well and operated by `the rise and fall of the level of liquid in the well, the other of said switches being operated by the means for raising and lowering the wire line, and means operated by the delivery of a slug of oil to the top of the well for controlling movement of the wire line in the opposite direction.

2. In a gas lift pump of the type wherein a reciprocable member is alternately raised and lowered in a well for controlling the operation if a bottom hole\ gas Valve, the improvement which comprises an accumulation chamber, an eductor tube in said chamber through which the member is adapted to be raised and lowered, a control valve in the wall of said chamber and control valve operating means in the wall of the eductor tube opposite the control valve, said control valve operating means being arranged for actuation by the reciprocable member.

3. Thesubject matter of claim 2 in which the reciprocable member is a hollow tube.

4. In a gas lift pump of the type wherein a l wire line suspended sinker is alternately raised and lowered in a well for controlling the operation of a bottom hole gas valve, the improvement which comprises an accumulation chamber in the well, an eductcr tube in said chamber through which the sinker is adapted to vbe raised and lowered, a control valve in the Wall of said chamber, control valve operating means in the wall of said eductor tube opposite the control valve, said control valve operating means being arranged for actuation by the sinker, power means adapted for operation to raise the sinker, an electrical circuit for controlling the operation oi the power means and a float switch in said electric circuit, carried by the wire line, said switch being located in the tubing and vertically spaced from said sinker at a predetermined level relative thereto and arranged for operation upon rise of well liquid in the tubing to said level to cause operation of the power means.

5. In an intermittent gas lift system for wells including a string of tubing extending down the well, a normally closed gas control valve in the tubing, a member reciprocable in the 'tubing to open the valve and power means for raising said member, the improvement which comprises an electrical control circuit for controlling the operation of the power means, said circuit including a oat operated electric switch associated with said member for reciprocation in the tubing therewith, said switchbeing adapted for operation by the liquid in the tubing.

6. The subject matter of claim 5 wherein the reciprocable member is a hollow tube.

7. In an intermittent gas lift system for recovering liquids from wells, including a string of tubing extending from the surface down the well to a point beneath the level of the liquid therein, a gas control valve in the tubing and power driven means adapted for operation to move said valve from one operating position to another, the improvement which comprises an electrical control circuit for controlling the operation of the power means, said circuit including an electric switch in the tubing, said switch being actuated by the liquid in the tubing at a predetermined level of the liquid and being removably positioned at said level, and means Vfor positioning and removing the switch fromsaid level by simply lowering and raising the same through the tubing.

8. In an intermittent gas lift system for wells including a string of tubing extending down the well. a normally closed gas control valve in the tubing, a reciprocal member in the tubing adjacent the valve and power means at the surface adapted for operation to move said member to open the valve, the improvement comprising an electric circuit for controlling the operation of the power means, said circuit including a float actuated switch in the tubing adapted to be actuated by the rise of the level of the liquid in the tubing, and means extending to the top of the well for adjustably locating the switch relative to the tubing and the liquid in the tubing, at any desired level for actuation of the switch by the rise of liquid to said level.

9. In an intermittent gas lift system for wells including a string of tubing extending down the well, a normally closed gas control valve in said tubing, a sinker reciprocable in the tubing to operate the valve, power means at the surface of the well, and a cable connecting the sinker with the power means for raising and lowering the sinker, the improvement comprising an electrical control circuit for controlling the operation of the power means, a float operated electric switch in said circuit, said switch being adapted to be suspended in the tubing by said cable in fixed spaced relation to the sinker and adapted for operation by the rise of liquid in the tubing to a predetermined level, and means whereby said sinker and switch may be removed from the tubing to the surface for changing said xed spaced relation and thereafter replaced in the tubing by simply raising and lowering the same through the tubing.

ROBERT L. KIRKPATRICK. 

